Carbonated beverages are currently stored in a variety of sizes and shapes of containers, including traditional glass bottles, metal cans, and, more recently, large plastic containers. Carbonation in the beverage is sufficiently retained so long as the container remains sealed. Once a container has been opened, however, carbonation rapidly escapes even if a container is reclosable. When most of the carbonation has escaped from the beverage, the beverage becomes "flat" and is undesirable for consumption.
Resealable caps are frequently employed on larger soft drink containers so as to preserve carbonation. However, the beverage still tends to lose carbonation even when recapped. The loss of carbonation has been attributed to the volume of air trapped within the container above the surface of the beverage. Because of the principle of dynamic equilibrium of liquid to vapor, carbonation in a beverage diminishes in proportion to the surface area of the beverage exposed to the air as well as the effective volume of air above the surface. While capping the bottle with a sealing device such as a cap or stopper may retard the loss of carbonation, carbonated beverages still tend to lose carbonation if the container is repeatedly opened and reclosed.
Various types of collapsible containers are known in the art. For example, U.S. Pat. No. 3,946,903 discloses a collapsible, spirally fluted container for dispensing viscous material. It is not believed that this container would be suitable for soft drinks since the amount of plastic material required to create the spiral flutes would make the container inordinately expensive and therefore undesirable. Many various types of collapsible containers for viscous materials are known in the art, for example U.S. Pat. Nos. 2,268,993, 2,250,022, 2,129,120, 2,009,761, 972,095, and 687,790. While these types of collapsible containers are quite suitable for thick, viscous materials such as paint, toothpaste, cold cream, and the like, many of these containers are made from metal and are thus inappropriate for soft drinks, or are susceptible to axial tilting. For example, soft drink containers must be able to stand upright. Containers designed for viscous materials typically are not designed to stand upright and consequently should the container be filled with a fluid material instead of a viscous material, the container would have a tendency to "flop" over, which would be undesirable.
Accordingly, there is a need for an improved collapsible container for carbonated beverages such as soft drinks which does not suffer from these problems in prior art collapsible containers.